Camera module

ABSTRACT

Disclosed herein is a camera module in which a movement of a magnet is controlled by only magnetic force between the magnet and a yoke without a spring for controlling the movement of the magnet which operates up and down. The camera module includes: a lens module; and a main frame supporting the lens module and allowing the lens module to be driven in an optical axis direction, wherein the lens module includes: a lens assembly including a plurality of lenses; and a magnet fixed to one side of the lens module, and the main frame includes: a coil facing the magnet, fixed to one side within the main frame, and generating an electric field as power is applied thereto; and a yoke disposed to face the magnet with the main frame and the coil interposed therebetween and controlling driving of the lens module by attraction with the magnet.

CROSS REFERENCE(S) TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 119 ofKorean Patent Application Serial No. 10-2012-0057542, entitled “CameraModule” filed on May 30, 2012, which is hereby incorporated by referencein its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a camera module, and more particularly,to a camera module in which a movement of a magnet is controlled usingonly the attraction between the magnet and a yoke without a spring forcontrolling the movement of the magnet which operates up and down.

2. Description of the Related Art Recently, in line with the developmentof digital camera manufacturing technologies, mobile communicationterminals equipped with a compact and lightweight camera module has beenreleased.

A camera includes a plurality of lenses for focusing and zoomingfunction, and focusing is adjusted by adjusting relative distancesbetween the plurality of lenses. A driving unit of a mobilecommunication terminal for auto-focusing serves to adjust focus to animage sensor by moving a lens in an optical axis direction. A cameramodule including such a driving unit is required to be firmly operatedover external impact, but as terminals have been increasinglymultifunctional and compact, the size of a camera module is reduced,resulting in a camera module that is vulnerable to external impact.

In the related art, in order to lessen external impact, a stopper isinstalled on upper and lower portions of a camera module and a bufferingmember is added to the stopper, but this method has a problem in whichan additional component should be used, which does not allow a camera tobe reduced in size. An elastic member based on pre-load is used toalleviate external impact, but here, since the pre-load should beconstantly applied in a direction opposite to a direction in which alens is driven, power consumption is increased.

SUMMARY OF THE INVENTION

An object of the present invention is to reduce the size of a cameramodule by reducing a speed of a driving unit by only the attractionbetween a magnet and a yoke, without using stoppers otherwise installedat upper and lower portions of the camera module, to thus lessen impactand eliminate the use of an additional component, and to preventunnecessary power consumption by eliminating an elastic membercorresponding to pre-load.

According to an exemplary embodiment of the present invention, there isprovided a camera module including: a lens module; and a main framesupporting the lens module and allowing the lens module to be driven inan optical axis direction, wherein the lens module includes: a lensassembly including a plurality of lenses; and a magnet fixed to one sideof the lens module, and the main frame includes: a coil facing themagnet, fixed to one side within the main frame, and generating anelectric field as power is applied thereto; and a yoke disposed to facethe magnet with the main frame and the coil interposed therebetween andcontrolling driving of the lens module by attraction with the magnet.

When the lens module is positioned at the highest point in the opticalaxis direction, the uppermost end portion of the yoke may be positionedbetween the uppermost end portion and the lowermost end portion of themagnet.

Force driving the lens module upwardly in the optical axis direction maybe equal to the attraction between the magnet and the yoke.

When the lens module is positioned at the lowermost point in the opticalaxis direction, the lowermost end portion of the yoke may be positionedbetween the uppermost end portion and the lowermost end portion of themagnet.

Force driving the lens module downwardly in the optical axis directionmay be equal to attraction between the magnet and the yoke.

The camera module may further include: a support member having a V or Ushape and fixed to one lateral surface or both lateral surfaces of anouter side of the lens module so as to be formed in the optical axisdirection; and a guide member fixed within the main frame andaccommodating the support member having the V or U shape such that thelens module moves in the optical axis direction.

The camera module may further include: a position sensor positionedwithin a winding of the coil and sensing a position of the magnet.

A plurality of magnets and a plurality of yokes may be provided.

The camera module may further include: a plate spring positioned at alateral lower portion within the main frame and providing restoringforce to the lens module at a point lower than a lower critical point inan optical axis direction in which the lens module is driven.

The camera module may further include: a plate spring positioned at alateral upper portion within the main frame and providing restoringforce to the lens module at a point higher than an upper critical pointin an optical axis direction in which the lens module is driven.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a camera module according to anembodiment of the present invention.

FIG. 2 is a cross-sectional view of the camera module according to anembodiment of the present invention.

FIGS. 3A and 3B are views illustrating attraction between a magnet and ayoke according to a vertical movement of the camera module according toan embodiment of the present invention.

FIGS. 4A and 4B are graphs showing a comparison of attraction betweenthe magnet and the yoke according to an embodiment of the presentinvention and a related art.

FIGS. 5A and 5B are cross-sectional views of a camera module accordingto another embodiment of the present invention.

FIGS. 6A and 6B are cross-sectional views of a camera module accordingto another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.However, this is only by way of example and therefore, the presentinvention is not limited thereto.

When technical configurations known in the related art are considered tomake the contents obscure in the present invention, the detaileddescription thereof will be omitted. Further, the followingterminologies are defined in consideration of the functions in thepresent invention and may be construed in different ways by theintention of users and operators. Therefore, the definitions thereofshould be construed based on the contents throughout the specification.

As a result, the spirit of the present invention is determined by theclaims and the following exemplary embodiments may be provided toefficiently describe the spirit of the present invention to thoseskilled in the art.

Hereinafter, the exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings.

FIG. 1 is a perspective view of a camera module according to anembodiment of the present invention. FIG. 2 is a cross-sectional view ofthe camera module according to an embodiment of the present invention.

With reference to FIGS. 1 and 2, a camera module 100 according to anembodiment of the present invention may include a lens module 120; and amain frame 150 supporting the lens module 120 and driven in an opticalaxis direction. The lens module 120 may include a lens assembly 122including a plurality of lenses; and a magnet 121 fixed to one side ofthe lens module 120. The main frame 150 may include a coil 161 facingthe magnet 121, fixed to one side of the main frame 150 within the mainframe 150, and generating an electric field when power is appliedthereto; and a yoke 160 facing the magnet 121 with the main frame 150and the coil 161 interposed therebetween and controls driving of thelens module 120 by attraction with the magnet 121. In this case, aplurality of magnets 121 and a plurality of yokes 160 may be provided.

Having the yoke 160, the main frame 150 concentrates an electric fieldgenerated when power is applied to the coil 161 and a magnetic field ofthe magnet 121 to a space between the coil 161 and the magnet 121. Whenpower is not applied to the coil 161, attraction may be generatedbetween the magnet 121 and the yoke 160. When the lens module 120 isdriven up and down in the optical axis direction in a state in whichpower is not applied to the coil 161, attraction is generated in adirection opposite to the direction in which the lens module 120 isdriven between the magnet 121 and the yoke 160 from an upper criticalpoint or a lower critical point with respect to the optical axisdirection in which the lens module 120 may be driven, so driving of thelens module may be controlled. Here, the upper critical point or thelower critical point may refer to a point at which the lens module 120may collide with other components to receive impact first when normallydriven in the optical axis direction. Details thereof will be describedhereinafter.

When viewed in the optical axis direction, an upper portion of the mainframe 150 may include an opening 111 having the same shape as a shape ofthe lens module 120 viewed from above so as to be coupled with the lensmodule 120, and an opening 111 may be formed on a lower portion of themain frame 150 in order to transmit electrical signal of a subject to acontroller (not shown) of the lens module 120. Thus, the main frame 150may serve to house the lens module 120.

The camera module 100 may further include a support member 125 having aV or U shape and fixed to one lateral surface or both lateral surfacesof an outer side of the lens module 120 so as to be formed in theoptical axis direction; and a guide member 155 fixed within the mainframe 150 and accommodating the support member 125 having the V or Ushape such that the lens module 120 moves in the optical axis direction.

The lens module 120 may include the lens assembly 122. The lens assembly122 may include a plurality of focusing lenses, and diameters andcurvatures of the plurality of lenses may be different within a rangerequired for the performance of the product. The plurality of lenses maybe assembled within the lens module 120.

The camera module 100 may further include a position sensor 162positioned within a winding of the coil 161 and sensing the position ofthe magnet 121. In this case, the position sensor 162 may sense aposition of the magnet 121 in the optical axis direction. Namely,sensing a position of the magnet 121, the position sensor 162 may senseand detect a change in a position of the lens module 120 and generate acontrol signal required for focusing.

The coil 161 may be wound to face the magnet 121 such that it interactswith the magnet 121 to generate driving force based on electromagneticforce. The camera module 100 may further include a cover glass 171 andan image sensor 172. When a user presses an image capture button, theimage sensor 172 operates and then an image of a subject may passthrough the lens assembly 122 so as to be changed into an electricalsignal in the image sensor 172, and the electrical signal may betransmitted to a controller (not shown) within the camera module 100. Ifthe image of the subject is dim, the electrical signal may be set to beweak and, in this case, it may be determined that there is an error infocusing the lens assembly 122 and a current for moving the lens module120 in the optical axis direction may be applied to the coil 161.Namely, an electrical field generated as a current is applied to thecoil and a magnetic field of the magnet 121 interact to move the lensmodule 120 up and down in the axial direction, thus focusing the lensassembly 122.

The camera module 100 may further include a cover 110 covering the upperend portion of the lens module 120. The cover 110 may include theopening 111 formed in a penetrative manner in the optical axisdirection. Since the opening 111 provides an image capture path withrespect to the lens module 120, the lens module 120 may capture an imageof a subject through the opening 111.

The cover 110 may include a binding piece 112, and the main frame 150may include a binding recess 152 to be coupled with the binding piece112. The binding piece 112 may be formed on edges at both sides of thecover 110 in a facing manner and include a binding hook formed bycutting away a portion thereof. The binding hook may have an inwardlybent shape. In order to be coupled with the cover 110, the main frame150 may have a binding recess 152 formed on an outer surface thereof,and a hook recess may be formed in the binding recess 152. When thecover 110 is coupled to the main frame 150, the binding piece 112 isaccommodated in the binding recess 152 and, in this case, the bindinghook may be coupled to the hook recess so as to be bound to the hookrecess.

FIGS. 3A and 3B are views illustrating attraction between the magnet 121and the yoke 160 according to a vertical movement of the camera module100 according to an embodiment of the present invention. FIGS. 4A and 4Bare graphs showing a comparison of attraction between the magnet 121 andthe yoke 160 according to an embodiment of the present invention and arelated art.

An impulse I of an object may be expressed by I=F*t=m*v (m is a mass ofthe object and v is a velocity of the object). Namely, noise and damageof the object by impact is proportional to the impulse, and according tothe above formula with respect to an impulse of the object, when themass of the object is reduced or when the velocity of the object isreduced, the impulse of the object may be reduced. Thus, according to anembodiment of the present invention, an impulse with respect to the lensmodule 120 may be reduced by reducing a driving velocity of the lensmodule 120 due to external impact. Here, in the camera module 100according to an embodiment of the present invention, an impulse withrespect to the lens module 120 is intended to be reduced by reducing thevelocity of the lens module 120 by only attraction between the magnet121 and the yoke 160.

When the lens module 120 is positioned at the highest point in theoptical axis direction, it may mean that the lens module 120 is at theupper critical point as mentioned above. Namely, the highest point orthe upper critical point of the lens module 120 in the optical axisdirection may refer to a point at which the lens module 120 mayinitially receive impact due to a collision with other components whenthe lens module 120 is driven upwardly in the optical axis direction.Similarly, when the lens module 120 is positioned at the lowest point inthe optical axis direction, it may mean that the lens module 120 is atthe lower critical point as mentioned above. Namely, the highest pointor the lower critical point of the lens module 120 in the optical axisdirection may refer to a point at which the lens module 120 mayinitially receive impact due to a collision with other components whenthe lens module 120 is driven downwardly in the optical axis direction.

With reference to FIG. 3A, when the lens module 120 is positioned at thehighest point in the optical axis direction, an upper end portion of theyoke 160 may be positioned between the uppermost end portion and thelowermost end portion of the magnet 121.

When the uppermost end portion of the yoke 160 is positioned between theuppermost end portion and the lowermost end portion of the magnet 121,attraction between the yoke 160 and the magnet 121 may act in thedownward direction Fy and in a vertical direction Fx, respectively.Resultant force F as shown in FIG. 3A may act as the vector sum of theattraction in the downward direction and the attraction in the verticaldirection. In this case, force by which the lens module 120 is drivenupwardly in the optical axis direction may be equal to the attraction Fbetween the magnet 121 and the yoke 160. Thus, the lens module 120 maybe freely driven between the upper critical point and the lower criticalpoint, and here, even if impact is strong enough to release the lensmodule 120 from the upper critical point is applied to the lens module120, the lens module 120 is not released from the upper critical pointdue to the attraction between the magnet 121 and the yoke 160, so thatthe lens module is not damaged by external impact.

Similarly, with reference to FIG. 3B, when the lens module 120 ispositioned at the lowest point in the optical axis direction, andlowermost end portion of the yoke 160 may be positioned between theuppermost end portion and the lowermost end portion of the magnet 121.

When the lowermost end portion of the yoke 160 is positioned between theuppermost end portion and the lowermost end portion of the magnet 121,attraction between the yoke 160 and the magnet 121 may act in the upwarddirection Fy and in a vertical direction Fx with respect to the opticalaxis direction, respectively. Resultant force F as shown in FIG. 3B mayact as the vector sum of the attraction in the upward direction and theattraction in the vertical direction. In this case, force by which thelens module 120 is driven downwardly in the optical axis direction maybe equal to the attraction F between the magnet 121 and the yoke 160.Thus, the lens module 120 may be freely driven between the uppercritical point and the lower critical point, and here, even if impactstrong enough to release the lens module 120 from the lower criticalpoint is applied to the lens module 120, the lens module 120 is notreleased from the lower critical point due to the attraction between themagnet 121 and the yoke 160, such that the lens module is not damaged byexternal impact.

FIG. 4A is a graph of restoring force of the related art camera module,and FIG. 4B is a graph of restoring force of the camera module accordingto an embodiment of the present invention. Here, restoring force mayrefer to force that will return the lens module 120 in a directionopposite to the driving direction based on external impact. Namely, therestoring force may refer to the attraction F between the magnet 121 andthe yoke 160 as described above. With reference to a portion indicatedby the dotted line in FIG. 4B, it can be seen that as the position ofthe lens module 120 is closer to the highest point, restoring force issharply increased. Namely, as the lens module 120 moves to be closer tothe upper critical point as described above by external impact,attraction between the magnet 121 and the yoke 160 is increased, andresultantly, the absolute value of the attraction and that of the sizeof force by the external impact are equal at the upper critical point,and thus, driving of the lens module 120 by external impact may bestopped. This is the same when the lens module 120 is close to the lowercritical point by external impact as described above.

FIGS. 5A-5B and 6A-6B are cross-sectional views of a camera moduleaccording to another embodiment of the present invention.

With reference to FIGS. 5A and 5B, the camera module may further includea plate spring 280 positioned at a lateral lower portion within a mainframe 250 and providing restoring force to a lens module 220 at a pointlower than a lower critical point in an optical axis direction in whichthe lens module 220 may be driven. The plate spring 280 may physicallyprevent the lens module 220 from being released from the lower criticalpoint when the lens module 220 is driven downwardly in the optical axisdirection by external impact. Namely, the plate spring 280 may serve toprevent the lens module 220 from being released from the lower criticalpoint together with attraction between the magnet 221 and the yoke 260.

Similarly, with reference to FIGS. 6A and 6B, the camera module mayfurther include a plate spring 380 positioned at a lateral upper portionwithin a main frame 350 and providing restoring force to a lens module220 at a point higher than an upper critical point in an optical axisdirection in which the lens module 220 may be driven.

According to the exemplary embodiments of the present invention, amovement speed of the lens module is reduced by only attraction betweenthe magnet and the yoke, without having to install a stopper forlessening impact with respect to the lens module at upper and lowerportions of the camera module, whereby the use of an additionalcomponent can be eliminated, reducing production unit costs and reducingthe size of the camera module.

In addition, since impact is lessened by reducing the speed of the lensmodule only through attraction between the magnet and the yoke, anelastic member based on a pre-load can be eliminated, thus preventingpower consumption due to the pre-load.

Although the exemplary embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

Accordingly, the scope of the present invention is not construed asbeing limited to the described embodiments but is defined by theappended claims as well as equivalents thereto.

What is claimed is:
 1. A camera module comprising: a lens moduleincluding a lens assembly; a main frame accommodating the lens moduletherein; a driving part comprising a magnet and a coil that areconfigured to generate a driving force that drives the lens module in anoptical axis direction; and a yoke fixed to the main frame, wherein whenthe lens module is driven in the optical axis direction in a state whichpower is not applied to the coil, a velocity of the lens module iscontrolled by attractive force between the magnet and the yoke.
 2. Thecamera module according to claim 1, wherein as the lens module is drivento be closer to an object or an image sensor, the velocity of the lensmodule is reduced by the attractive force between the magnet and theyoke.
 3. The camera module according to claim 1, wherein as the lensmodule is driven to be closer to an object or an image sensor, theattractive force between the magnet and the yoke is increased.
 4. Thecamera module according to claim 1, wherein the velocity of the lensmodule is controlled by a sum of attractive force generated in theoptical axis direction and attractive force generated in a directionperpendicular to an optical axis.
 5. The camera module according toclaim 1, further comprising a position sensor sensing a position of themagnet.